Orientation devices of what is called “two axis” orientation head or turret type, for orienting at least one transmission assembly for transmitting at least one optical and/or electromagnetic beam in elevation and/or in bearing, by rotation of said transmission assembly about an elevation axis and/or a bearing axis respectively are already known.
In these known turrets, the transmission assembly, for example an optical block based on mirrors or prisms, which is capable of receiving an incident light beam to be deflected in order to produce a transmitted beam, is mounted so as to pivot on a fork about a first axis, called the elevation axis, and capable of being rotated about said elevation axis by a first motor supported by said fork, which fork is mounted so as to pivot on a base about a second axis, called the bearing axis, perpendicular to the elevation axis, and capable of being rotated about said bearing axis by a second motor supported by said base, which is mounted on a platform that may be a terrestrial and stationary platform or may be a moving platform mounted on a terrestrial vehicle, a ship or an aircraft.
On existing orientation devices of this type, the two motors are rotary electric motors, that is to say conventional electromagnetic motors, which may be torque motors or stepper motors.
To deliver high torques needed to obtain sufficient angular accelerations and/or angular velocities to obtain homing times of an orientation turret over a given sector in space that are appropriate to the various envisaged optronic functions, these motors are heavy and bulky, hence a large inertia of the turret, thereby having a negative impact on the desired performance characteristics. In addition, to increase the delivered torque while keeping the electric motors within reasonable weight and volume ranges, the drive for the parts moving in elevation and in bearing is provided by the electric motors via transmissions with mechanical speed reducers. However, the use of mechanical reducers, which are necessary in the motor drive units of orientation turrets currently employed, incurs, in turn, drawbacks in terms of costs, the presence of dry friction, anti-backlash means and also servocontrol in order to compensate for the drawbacks, that is to say to guarantee as precise a positioning as possible of a beam, in particular an optical beam, emitted by the orientation turret.
Admittedly, the use of torque motors makes it possible to avoid speed and backlash reducers, however these motors do not have a torque/mass ratio which is high to the point of allowing a volume and mass reduction propitious to the use of an orientation turret having torque motors on small platforms (aircraft or terrestrial vehicles) by the natural integrability of such a turret.
When the electric motors of existing orientation turrets are stepper motors, their essential drawback is that the elementary step of these motors is not small enough, thereby resulting in a lack of precision in the orientation of the turrets.
Thus, the use of electromagnetic motor drive units entails a mass, a volume, an energy consumption and a cost that it would be advantageous to reduce, these parameters being crucial in systems onboard aircraft, or in terrestrial vehicles in which space is limited.
Existing orientation devices of this type, based on the use of conventional technologies, therefore do not make it possible to achieve the desired performance characteristics as mentioned above, namely high angular coverage with very high precision and very high aiming velocity, simultaneously with low volumes, masses and costs, advantageously enhanced by great structural simplicity, in particular because the conventional motor drive technologies do not allow a high torque/mass ratio to be achieved except at the cost of a mass and volume performance that does not permit integration in an orientable turret having a structure suitable for the applications and uses envisaged by the present application. Specifically, for such orientation turrets, the optomechanical architecture must exhibit compactness and centring characteristics that are propitious to the equilibrium and to the general compactness an orientation device according to the present invention.